1. Field of the Invention
The present invention relates to a polyvinyl chloride resin composition for powder molding and also to a process for producing the same.
2. Description of the Prior Art
The recent trend in the automotive interior covering materials for crash pad, armrest, headrest, console box, meter hood, door trim, etc. is toward those materials which are light in weight, soft to the touch, and have a high quality appearance provided by embossing which resembles a leather-like finish and a stitch-like pattern.
These covering materials are conventionally produced by the powder slush molding method which consists of contacting a powder composition with a heated mold, thereby causing particles to fuse together, and removing excess powder remaining unfused, said powder composition being formed by dry-blending polyvinyl chloride resin, plasticizer, stabilizer, pigment, etc.
The product of powder slush molding is usually backed with a polyurethane layer to be made into a covering material. The thus obtained covering material has the disadvantage of poor adhesion between the polyvinyl chloride resin layer and the polyurethane layer.
In order to overcome this disadvantage, there has been proposed an improved powder slush molding method which employs a polyvinyl chloride resin composition containing polypropylene glycol or a modified product thereof, i.e., polyether polyol (Japanese Patent Kokai No. 136542/1986).
This molding method, however, is not satisfactory because the resin composition does not adhere uniformly to the mold or the excess of the resin composition is not removed uniformly after fusing. Thus the resulting molded article greatly fluctuates in thickness and has an irregular back surface.
With the foregoing in mind, the present inventors carried out a series of experiments which led to the finding that it is possible to produce a covering material which has uniform thickness and good adhesion to the polyurethane layer if the resin composition for powder molding is incorporated with a specific compound, that is, saccharide. The present invention was completed on the basis of this finding.